Objective: To develop and test a web-based Clinical Decision Support System (CDSS) tool, which integrated a new fuzzy multiple criteria classification methodology named PROAFTN in acute leukemia (AL) diagnosis. <br /><br />Methods: We have integrated a PROAFTN method and developed a web-based clinical decision support system using standard JSP, servlets, and XML technologies. All website data are database-driven; and the database system can handle data store, update, and retrieval instantly. Since the system was moved to a web server, we have started our experimental testing on 191 AL cases. <br /><br />Results: The percentage of correct classification in this experimental testing was consistent with the proposed prototype. 96.4% of AL cases were correctly classified, proving that web-integration can be a promising tool for dissemination of CDSS tools. We found our system to be robust and capable of deployment for referring physicians. <br /><br />Conclusions: Our experimental results suggest that the Internet has promise as a means for distribution of CDSS tools. This system will help to: 1) make a “virtual” diagnosis and to compare its performances with given clinical diagnosis; 2) exchange health information between physicians and hematologists at the location and time of need; 3) assist online learning and simulate cases for training practitioners; 4) implement a strict security and access control for transmission of electronic health data through the Internet. The method will not replace specialists, but was developed to assist biologist-hematologists and general practitioners remotely in making decisions on medical diagnosis.